Method and device for measuring fluctuations in the cross-sectional area of hair in a pre-determined scalp area

ABSTRACT

The method for isolating an area of hair-bearing skin and measuring a combined cross section of hair in the area comprising the steps of: preparing a pre-measured site on the scalp; isolating a standardized bundle of uncut hair at the site; compressing the bundle of hair with a measurable load while simultaneously measuring the height of the bundle of hair with a piston and cylinder device. One embodiment of the device comprises a body having a slot for receiving a bundle of hair, an anvil positioned adjacent said slot, and a mechanism for causing relative movement between the body having the slot and the anvil thereby to compress a bundle of uncut hair received in the slot against the anvil.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a method and device for measuringfluctuations in the cross sectional area of a bundle of hair for thepurpose of documenting the clinical course of medical hair lossdisorders and the effectiveness of hair growth treatments and/or for thepurpose of indirectly calculating the severity of balding disorders orefficacy of hair growth treatment as evidenced by a decrease or increasein hair population and/or hair shaft diameter.

2. Description of the Related Art

Heretofore, a hair volume-measuring device used for measure of hairdamage was disclosed in the Kabacoff et al. U.S. Pat. No. 4,665,741.

Hair shedding is a condition characterized by loss of hairs ofnormal-sized diameters. It is one of the two major categories of hairloss. Shedding is diffusely distributed over the scalp and may be thesign of several medical abnormalities and toxicities. It mayphysiologically follow high fever, cessation of birth control pills, orchildbirth. Shedding is characterized by the appearance of skin on thescalp where hair was once present. Shedding may be quantified bymeasuring the density of hairs present in an area of one-centimetersquare of scalp. Hair density usually is measured by closely cutting thescalp hair (about 2 mm long in an area 5 mm×5 mm) and then counting theremaining cut hairs present on the scalp and multiplying that valuetimes 4. The hair density of normal individuals in the absence ofshedding ranges between 120 to 200 hairs per sq cm of scalp.

Hair thinning is a condition characterized by the gradualminiaturization of individual scalp hairs. It is the second majorcategory of hair loss. The appearance of hair loss is the result ofdecreasing diameters resulting in the eventual absence of hairs.Thinning (like shedding) also is characterized by the appearance of skinon the scalp where hair was once present. Thinning affects an estimated75% of men and 10% of women. Unlike shedding, it is not diffuse in itsdistribution over the entire scalp surface, but almost always appears ina pattern, with hair loss on the top of the scalp. Thinningcharacteristically spares the posterior and sides of the lower scalp,creating a familiar horse-shaped fringe that persists in spite of themost advanced cases.

Thinning occurs in healthy individuals and is referred to as balding,pattern balding, male or female pattern alopecia, androgenctic alopecia,male or female pattern balding. It is considered normal in 75% of men.And, although it may occur in healthy women, it may indicate anendocrine abnormality in a small group of women.

Early pattern balding is difficult to recognize and difficult toquantify. Simple density measurements (as performed in shedding) are oflittle value because there is a mixed population of both normal-sizedand miniaturized hairs. When density counts are performed, a normal andminiaturized hair would each be counted as one hair. Therefore, in orderto detect and quantify thinning in a meaningful manner, the actual hairmass (the collective cross sections of hair from a predetermined area ofscalp) must be measured. This alone would reflect the density of hairsand the array of mixed diameters that are present.

In order to quantify pattern and diffuse hair loss, scientists havecommonly used three basic methods:

-   -   1. Hair density count    -   2. Clinical photography    -   3. Hair weight.

Quantification of hair loss by measuring the collective cross sectionsin a pre-determined area of scalp has not been reported in thescientific literature nor disclosed in prior U.S. Patents.

The three commonly used methods are described in more detail below:

Density count: The density of an area of scalp is compared to the knownnormal range of values, which is 120 to 200 hairs per sq cm. Todetermine the percent loss of density for a single individual, thedensity on the top part of the scalp (the area of loss) may be comparedto the density on the lower back and sides (the normal and permanenthair zone). The percent hair loss is calculated by dividing the haircount in the hair loss area by the hair count in the permanent zone.This method is quite imprecise in conditions of thinning, because itmeasures only the number of hairs and makes no allowance for theirvariations in diameter. The method is used however because it is a bitmore precise than clinical photography. It requires cutting off hair anddirect scalp exam with a hand lens or video microscope.

Clinical photography: Photography is performed comparing the patient'shair loss area to the permanent zone. It may also compare the patient'shair loss zone to a picture of the same zone of a patient with no hairloss, or of a prior or subsequent state of loss in the same patient. Inthis manner, the growth or loss is grossly quantified by visualobservation alone. No insight is gained into whether or not the hairloss is the result of thinning or shedding. Photography is quiteimprecise and obscured by various hairstyles and hair lengths. It ishowever the most common form of hair loss documentation because it israpid, requires not special training and is easily archived. It does notrequire the cutting of hair, but does require standard photo equipmentlighting, positioning of hair, and standardized hair length, to yieldany kind of comparable data.

Hair weight: A small area of hair (usually 5 mm×5 mm) is shaved from abalding area. The patient returns in 30 days and the newly grown hair iscut and weighed. The value is compared to a subsequent similar assay ofthe same area. In cases of pattern loss, the procedure may be performedin the permanent zone (lower posterior and lateral horseshoe shapedzone) and compared to the value in the thinning zone. The percent hairloss may be calculated by dividing the hair weight in the thinning areaby the hair weight in the permanent zone. Hair weight is a very precisemethod of measuring hair loss because it considers both the number ofhairs and their diameters and the hair length in its calculation. Itsdisadvantage is that the sample size represents a relatively smallsample of the scalp surface, and because it measures hair length aswell, it may not be as meaningful as thought.

Furthermore it is a very tedious process and impractical to perform in aclinical setting. It also requires cutting off hair. It is usedprimarily by commercial laboratories to measure the effectiveness ofhair-growing preparations i.e. finasteride, dutasteride, and minoxidil.

BRIEF SUMMARY OF THE INVENTION

According to the present invention there is provided a method and devicefor measuring fluctuations in the cross sectional area of a section ofhair as it relates to the quantification and clinical course of medicalhair loss disorders or the effectiveness or progress of hair losstreatment. The method and device are used for determining the cumulativecross-section of hairs within a pre-measured area.

The method and device uses a much larger sample of scalp surface thanthe hair weight method, hair count method, and hair cutting is notrequired. The length of the hair is not considered a factor in theevaluation because of wide variations of individual styling would makeit impossible, and clinically irrelevant. The method of the presentinvention is easy to perform in a non-laboratory setting and employs anew hand-held device. The method and device allow physicians and haircare professionals to track and document the status of patients,suffering from scalp hair thinning or shedding, at any time in thecourse of their evaluation or treatment. The method and device may beused to quantitatively evaluate the effectiveness of hair growingpreparations and drugs and quantify the severity and clinical course ofother medical hair loss disorders.

In practicing the method of the present invention, a predetermined areaof hair-bearing skin or scalp is isolated by any of several means.Typically a 2×2 cm of scalp hair is manually isolated using a comb orcombing element and fixed in place using 1×3″ gummed papers printed witha centimeter scale which are aligned and overlapped in the configurationof a 2×2 cm square. Alternatively, a 2×2 cm area may be isolated byusing any device that demarcates the periphery of the area, such as witha ruler and washable ink, marking pen, and/or using a simple comb-likedevice that is 2 cm. in length, which simultaneously bundles the hairand demarcates the perimeter of the area.

The bundle is snared by a lightweight spring-loaded hook-like (“J”shaped) arm which is drawn into a body of the device of the presentinvention. The device comprises a hair-trapping element including a “J”shaped end that extends through a boss and has a hair-receiving slot.The device further includes an anvil on an end surface of the bosspositioned adjacent the slot whereby relative movement between the “J”shaped end and the anvil compresses the hair received in the slot. Aheavyweight compression spring is provided in the device which bearsagainst the boss. Alternatively the device can have an anvil that movesinto a stationary slot.

The bundle is captured in the slot and automatically immobilized againstthe anvil on the boss. Preferably, the slot is 1 mm wide and 12 mm highand relative movement between the anvil and the slot measures the heightof the hair. By engaging the heavy compression spring, the load on thecolumn of trapped hair may be precisely maintained and thereby keptconstant in repeated measurements. This is important because the hairbundle is quite compressible. The mm height of the hair column isdisplayed on an LED window of an integrated micrometer head that causesrelative movement between the anvil and the slot. If a mechanical heightmeasuring gauge is incorporated in the design of the device, it isdisplayed on the face of an analog dial. If an electronic heightmeasuring gauge is incorporated into the device, the height is displayedon an LED window. The height of hair in the trapping hair-receiving slotis expressed as an arbitrary value that shall be called the hair mass,the hair mass index, the cross-sectional index, the cumulativecross-sectional index, or the combined cross-sectional index.

The method is performed in the hair thinning area and the permanent hairgrowth area of the scalp. The index value of the thinning area isdivided by the index value of the permanent area. The percent loss ofhair mass in the thinning area is thus derived. It is believed that themethod and device of the present invention may have profound medicalsignificance for the following reason: It is a known medical fact thatan individual must lose half of the hair in an area of the scalp, beforeit is obvious to the casual observer that any hair has been lost. Thiscan also be demonstrated by the casual observers inability to tell thedifference between a toupee with 200 hairs per sq cm and a toupee with100 hairs per sq cm. This observation however translates to thefollowing: By the time an individual realizes that he is “losing hair”he has already lost half of his hair! The device of the presentinvention enables hair professionals and physicians to measure the hairmass in the pre-balding normal-looking areas of the scalp and comparethese values to the hair mass value in the permanent zone. In this wayone can detect whether or not there is hair loss years before it isvisually obvious to the patient or his physician. The patient is alertedto the early hair loss and may enjoy the advantages of starting therapybefore the loss has significantly advanced. The method and device mayalso be used to track and quantify the progressive hair loss ofindividuals with untreated balding, or track and quantify thetherapeutic response of hair to drugs and devices that allegedly growhair.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

FIG. 1 is a top view of a scalp showing a section or bundle of hair thatis combed from a delineated section of scalp with a combing element andshows one side of the section of scalp being delineated by a gummedlabel.

FIG. 2 is a top view of a scalp showing a section or bundle of hair thatis combed from a delineated section of scalp and shows two sides of thesection of scalp being delineated by gummed labels.

FIG. 3 is a top view of a scalp showing a section or bundle of hair thatis combed from a delineated section of scalp and shows three sides ofthe section of scalp being delineated by gummed labels.

FIG. 4 is a top view of a scalp showing a section or bundle of hair thatis combed from a delineated section of scalp and shows four sides of thesection of scalp being delineated by gummed labels.

FIG. 5 is a plan view of one combing element.

FIG. 6 is a top plan view of the scalp shown in FIG. 4 and a deviceconstructed according to the teachings of the present invention formeasuring the cross-sectional area of the bundle of hair.

FIG. 7 is a top plan view of a scalp shown in FIG. 6 with a “J” shapedend of the device move toward a boss on the body of the device tomeasure the cross-sectional area of the bundle of hair positioned in aslot of the “J” shaped end.

FIG. 8 is a fragmentary enlarged view of the hair trapped in the slot ofthe “J” shaped end.

FIG. 9 is a cross-sectional view of the “J” shaped end taken along line9-9 of FIG. 8.

FIG. 10 is a cross-sectional view of a boss extending from the body ofthe device and in which the “J” shaped end is received.

FIG. 11 is a plan view of the device without a bundle of hair in theslot of the “J” shaped end, shows the “J” shaped end moved over theboss, and is broken away to show a heavy compression spring in the bodyof the device.

DETAILED DESCRIPTION OF THE INVENTION

Referring now to FIG. 1 there is illustrated therein a combed bundle orsection of hair 10 from a scalp 12, that has been combed with a comb orcombing element 14. The bundle 10 of hair is delineated from apredetermined area of the scalp 12 by a gummed label 16, without cuttingthe bundle 10 of hair.

As shown in FIGS. 2-4, sequentially the delineated area of the scalp isfixed by gummed labels 18, 20 and 22. Each gummed label has a centimeterscale printed thereon so that the predetermined area, e.g., 2 squarecentimeters, can be measured and segregated by the gummed labels 16, 18,20 and 22 from the rest of the hair on the scalp. The gummed labels 16,18, 20 and 22 are printed with lines at intervals 2 cm apart scale. Thecolor-coded lines are aligned with the edge of the preceding label andoverlapped in a 4 step sequential fashion to create an isolated field ofuncut hair that is 2 cm square.

Preferably, a 2×2 cm of scalp hair is manually isolated by combing thehair away from the designated square of hair-bearing scalp skin. This isdone in a sequential fashion as described above. Care is taken tomaintain a straight line at 90 degrees from the previous passage of thecombing element 14.

The combing element 14 is shown in FIG. 5 and has a predetermined tinearea 26, e.g., 2 cm. long, with tines 28 and an upwardly sloping topedge 29 extending to a handle 30.

A device 32 is provided, as shown in FIG. 6 for measuring the mass ofhair in a bundle 10 from the 2 sq cm area of a hair bearing skin orscalp and compares that hair mass to the hair mass per sq. cm. in apermanent (normal) zone on the scalp.

The device 32 is an electronic caliper 34 having a body 36 with anelectronic display 38 and a scale, gauge or analog display 40 forindicating the height or mass of hair in the hair bundle 10.

The device 32 includes a piston or plunger 42 that extends through thebody 36 and has a collar 43 thereon below a knob 44 at an outer end 46of the plunger 42. A light weight return spring 48 (FIG. 7) bearsagainst the collar 43 to urge the knob 44 away from an upper end 49 ofthe body 36 to push the plunger 42 upwardly. As shown a collar 50between the spring 48 and the upper end 49 of the body of the body 36 isprovided and has a reduced in diameter portion 51 that extends into thebody 36.

It will be understood that the scale, gauge or analog display 40 moveswith the plunger 42. Also, of course, the amount of movement of theplunger will be shown on the display 38.

The other end 52 of the plunger 42 has a “J” shape defined by a main leg53 and a hook leg 54 with a slot 56 therebetween. The slot 56 can be 1mm wide and 12 mm high.

The main leg 52 extends through a through bore 58 (FIG. 9) in a boss 60at a lower end 61 of the body 36.

As shown in FIG. 11 a heavy compression spring 62 in the body 36 bearsagainst a lower end 63 of the reduced in diameter portion 51 of thecollar 50.

A wall 64 of the boss 60 between the bore 58 and an outer surface 63 ofthe boss 60 is slidably received in the slot 56 upon relative movementbetween the boss 60 and the “J” shaped end 52.

The bundle of hair 10 is placed in the slot 56 and the knob 44 isscrewed down on the plunger 42 and moves the reduced in diameter portion51 of the collar 50 into the body 36 to compress the bundle of hair 10between a bottom 66 of the slot 56 and an end surface 68 of the wall 54(FIG. 9) with a predetermined compression established by the springconstant of the heavy spring 62 acting on the plunger 42. The endsurface 68 defines an anvil 68 against which the bundle 10 of hair iscompressed. In this way the device 32 defines a measuring devicecomprising the hair-holding slot 56, the “J” shaped end of thespring-loaded plunger 42 and the anvil 68.

The bundle or column 10 of hair is placed into the slot 66 andcompressed against the anvil 68 in order to measure its height of thecolumn or bundle 10 of hair. The anvil 68 and plunger are designed in amanner that always applies the same pressure to the column or bundle 10of trapped hair. (This is accomplished with the heavy compression spring62 bearing against the reduced in diameter portion of the collar 51)This is important because the hair bundle 10 is quite compressible. Themm height of the hair bundle or column 10 is read off a window on theelectronic display 38 and/or off of the scale gauge or analog display40. This arbitrary value shall be called the hair loss index or thedensity-diameter index. The procedure is performed in the balding areaand the permanent area. The value for the balding area is divided by thevalue for the permanent area. The percent loss of hair mass in thebalding is thus derived.

Oddly, in pattern balding (Androgenetic alopecia), the back and sides ofthe scalp are immune to the thinning process which doctors callminiaturization. So that on a balding scalp, the permanent horseshoeshaped fringe is populated with normal sized hairs (70 microns) with anormal density of 120-200 hairs per square cm. On the top of the scalp,in the areas of hair loss, the population of hairs ranges in size from70 microns to 15 microns in diameter with a wide range of hairs persquare cm.

The cumulative number of hairs per sq cm of scalp times their cumulativediameters equals a value that is best described as the hair mass. Whenthe hair mass value of the balding zone is divided by the hair massvalue of the normal permanent zone, the percent loss of hair mass in thebalding area is derived. When the hair mass value in an area of loss iscompared with a subsequent measurement of the same area at a time in thefuture, the percent hair loss or growth may be derived.

This information is very important to those who care for patients withhair loss, and those who develop drugs or devices that promote hairgrowth. Again it must be emphasized that although the length of the hairdoes contribute to the total visual mass of hair, it is not consideredbecause it varies with the cut length of the hair (styling) which has norelevance to intended application of this patent.

From the foregoing description, it will be understood that the methodand device of the present invention have a number of advantages, some ofwhich have been described above and others of which are inherent in themethod and device of the present invention.

Also modifications can be made to the method and device of the presentinvention without departing from the teachings of the present invention.

For example, a mark can be placed on the body 36 and another mark placedon the plunger 42 and a separate caliper can be used to measure thedistance between the marks for determining the height of hair compressedin the slot 56.

The heavy spring 62 can be omitted and the knob 44 can be tightened witha torque wrench to place a predetermined amount of compression on thebundle 10 of hair.

A simple protrusion with an anvil at the end can used in place of theboss 60 and received in the slot 56.

A simpler device can be provided including a body with the slot 56therein and a piston having the anvil 68 at one end can be provided andpositioned to be received in the slot 56. The body can be moved againstthe piston or the piston can be moved in and out of the slot 56.

The body and piston can be provided with a return spring, like spring48, for holding the anvil 68 in the slot 56 until the spring iscompressed to move the anvil 68 out of the slot 56.

If desired, side arms can be provided on the body, much like on asyringe, to facilitate gripping of the body while the piston or plungeris reciprocated or the knob 44 is rotated.

The non-isolated hair can be held down by other means, such as a ruleror hair clips instead of with gummed labels.

Further, the caliper can be mechanical or electrical electronic, can beattached to the body or plunger or can be separate from the device 32.

Accordingly, the scope of the invention is only to be limited asnecessitated by the accompanying claims.

1. An intravenous catheter introducing device comprising: a barrelhaving front and rear open ends opposite to each other in a longitudinaldirection, and a surrounding barrel wall which interconnects and whichis interposed between said front and rear open ends, said surroundingbarrel wall including a front smaller-diameter wall portion and a rearlarger-diameter wall portion which are opposite to each other in thelongitudinal direction and which are proximate to said front and rearopen ends, respectively, said surrounding barrel wall having an innerbarrel wall surface which surrounds an axis in the longitudinaldirection and which confines a passage that is communicated with saidfront and rear open ends, and an outer barrel wall surface opposite tosaid inner barrel wall surface in radial directions relative to theaxis; a needle cannula having a front segment terminating at a tip end,and a rear connecting end opposite to said front segment along the axis;a needle hub including a front holding portion and a rear shell portiondisposed opposite to each other along the axis, said front holdingportion being received in said passage so as to be surrounded by saidsmaller-diameter wall portion, said rear shell portion being insertedinto said passage from said rear open end, and being slidable relativeto said surrounding barrel wall along the axis between front and rearpositions to be proximate to said front open end and said rear open end,respectively, said front holding portion holding said rear connectingend of said needle cannula such that when said rear shell portion is inthe front position, said needle cannula is placed in a position of use,where said front segment extends forwardly of said front open end forready use, and when said rear shell portion is in the rear position,said needle cannula is placed in a disposal position, where said frontsegment retreats into said passage, said rear shell portion surroundingthe axis and defining a flashback chamber which is fluidly communicatedwith said needle cannula; a releasably retaining member which isdisposed to arrest axial movement of said needle hub relative to saidbarrel when said rear shell portion is in the front position, and whichincludes a retaining hole formed in said outer barrel wall surface ofsaid larger-diameter wall portion, and extending in a radial directionthrough said inner barrel wall surface, and an engaging peg disposed toextend in the radial direction, and engageable in said retaining hole toestablish an interengagement between said larger-diameter wall portionand said rear shell portion such that movement of said rear shellportion at the front position is arrested; an actuator operableexternally and disposed to enable said engaging peg to be disengagedfrom said retaining hole so as to permit the axial movement of saidneedle hub to the rear position; a catheter hub including a sleeveportion which is detachably sleeved on said smaller-diameter wallportion and which defines a duct along the axis, and a tip portion whichis opposite to said sleeve portion along the axis, and which defines athrough hole that is communicated with said duct along the axis and thatpermits extension of said front segment therethrough; and a tubularcatheter having a proximate segment which is inserted into said throughhole and which extends along the axis to be fluidly communicated withsaid duct, and a distal segment which extends from said proximatesegment along the axis to extend forwardly of said tip portion so as tosurround and sheathe said front segment of said needle cannula whilepermitting said tip end to project forwardly of said distal segment whensaid needle cannula is placed in the position of use.
 2. The intravenouscatheter introducing device of claim 1, wherein said needle hub furtherincludes an intermediate portion which interconnects said front holdingportion and said rear shell portion to communicate said needle cannulawith said flashback chamber and which is light transmissible to permitviewing of blood flowing therethrough.
 3. The intravenous catheterintroducing device of claim 2, wherein said needle hub further includesan air-permeable member which is in engagement with said rear shellportion so as to close said flashback chamber.
 4. The intravenouscatheter introducing device of claim 3, wherein said air-permeablemember is made from a porous filter material.
 5. The intravenouscatheter introducing device of claim 1, wherein said rearlarger-diameter wall portion has an elongated guideway extending fromsaid outer barrel wall surface through said inner barrel wall surface inthe radial direction, and elongated from said retaining hole rearwardlyand in the longitudinal direction to terminate at a rear retaining end,said engaging peg being disposed on and extending radially from saidrear shell portion to terminate at a shifted end which extends radiallyand outwardly of said outer barrel wall surface, and being slidablealong said elongated guideway from said retaining hole to said rearretaining end when said rear shell portion of said needle hub slidesfrom the front position to the rear position, said actuator beingconnected to said shifted end of said engaging peg, and being disposedoutwardly of and being slidable relative to said outer barrel wallsurface.
 6. The intravenous catheter introducing device of claim 5,wherein said elongated guideway has front and rear constricted regionswhich are formed immediately behind said retaining hole and immediatelyin front of said rear retaining end, respectively, such that once saidengaging peg is forced through one of said front and rear constrictedregions, movement of said engaging peg is arrested by virtue of asnap-fit in a corresponding one of said retaining hole and said rearretaining end so as to place said needle hub in a corresponding one ofthe front and rear positions.
 7. The intravenous catheter introducingdevice of claim 6, wherein said rear larger-diameter wall portionfurther has a split which extends from said rear retaining end of saidelongated guideway to said rear open end.
 8. The intravenous catheterintroducing device of claim 5, wherein said retaining hole includes aproximate connecting end and a distal retaining end which are oppositeto each other in a transverse direction relative to the longitudinaldirection and which are proximate to and distal from said elongatedguideway, respectively, such that said engaging peg is engaged in saiddistal retaining end to arrest movement of said rear shell portion ofsaid needle hub at the front position, and such that said actuator isoperated to move said engaging peg from said distal retaining end tosaid proximate connecting end so as to permit slidable movement of saidengaging peg along said elongated guideway. 9-14. (canceled)
 15. Anintravenous catheter introducing device comprising: a barrel havingfront and rear open ends opposite to each other in a longitudinaldirection, and a surrounding barrel wall which interconnects and whichis interposed between said front and rear open ends, said surroundingbarrel wall including a front smaller-diameter wall portion and a rearlarger-diameter wall portion which are opposite to each other in thelongitudinal direction and which are proximate to said front and rearopen ends, respectively, said surrounding barrel wall having an innerbarrel wall surface which surrounds an axis in the longitudinaldirection and which confines a passage that is communicated with saidfront and rear open ends, and an outer barrel wall surface opposite tosaid inner barrel wall surface in radial directions relative to theaxis; a needle cannula having a front segment terminating at a tip end,and a rear connecting end opposite to said front segment along the axis;a needle hub including a front holding portion and a rear shell portiondisposed opposite to each other along the axis, said rear shell portionbeing inserted into said passage from said rear open end, and beingslidable relative to said surrounding barrel wall along the axis betweenfront and rear positions to be proximate to said front open end and saidrear open end, respectively, said front holding portion holding saidrear connecting end of said needle cannula such that when said rearshell portion is in the front position, said needle cannula is placed ina position of use, where said front segment extends forwardly of saidfront open end for ready use, and when said rear shell portion is in therear position, said needle cannula is placed in a disposal position,where said front segment retreats into said passage, said rear shellportion surrounding the axis and defining a flashback chamber which isfluidly communicated with said needle cannula; a releasably retainingmember which is disposed to arrest axial movement of said needle hubrelative to said barrel when said rear shell portion is in the frontposition, and which includes a retaining hole formed in said outerbarrel wall surface of said larger-diameter wall portion, and extendingin a radial direction through said inner barrel wall surface, and anengaging peg disposed to extend in the radial direction, and engageablein said retaining hole to establish an interengagement between saidlarger-diameter wall portion and said rear shell portion such thatmovement of said rear shell portion at the front position is arrested;an actuator operable externally and disposed to enable said engaging pegto be disengaged from said retaining hole so as to permit the axialmovement of said needle hub to the rear position, said actuatorincluding a triggering member which is pivotally mounted on said outerbarrel wall surface at a fulcrum point, and which includes a weight endthat is formed integrally with said engaging peg, and that is disposedrearwardly of said rear shell portion so as to bring said engaging pegto abut against said rear shell portion when said needle cannula is inthe position of use, and a power end disposed at an opposite side ofsaid weight end relative to said fulcrum point so as to be actuated tomove said engaging peg in the radial direction to withdraw said engagingpeg from said passage, a biasing member which is disposed between saidrear shell portion and said inner barrel wall surface to bias saidneedle hub toward the rear position; a catheter hub including a sleeveportion which is detachably sleeved relative to said front holdingportion of said needle hub and which defines a duct along the axis, anda tip portion which is opposite to said sleeve portion along the axis,and which defines a through hole that is communicated with said ductalong the axis and that permits extension of said front segmenttherethrough; and a tubular catheter having a proximate segment which isinserted into said through hole and which extends along the axis to befluidly communicated with said duct, and a distal segment which extendsfrom said proximate segment along the axis to extend forwardly of saidtip portion so as to surround and sheathe said front segment of saidneedle cannula while permitting said tip end to project forwardly ofsaid distal segment when said needle cannula is placed in the positionof use.
 16. An intravenous catheter introducing device comprising: abarrel having front and rear open ends opposite to each other in alongitudinal direction, and a surrounding barrel wall whichinterconnects and which is interposed between said front and rear openends, said surrounding barrel wall including a front smaller-diameterwall portion and a rear larger-diameter wall portion which are oppositeto each other in the longitudinal direction and which are proximate tosaid front and rear open ends, respectively, said surrounding barrelwall having an inner barrel wall surface which surrounds an axis in thelongitudinal direction and which confines a passage that is communicatedwith said front and rear open ends, and an outer barrel wall surfaceopposite to said inner barrel wall surface in radial directions relativeto the axis; a needle cannula having a front segment terminating at atip end, and a rear connecting end opposite to said front segment alongthe axis; a needle hub including a front holding portion and a rearshell portion disposed opposite to and separated from each other alongthe axis, said rear shell portion being inserted into said passage fromsaid rear open end, and being slidable relative to said surroundingbarrel wall along the axis between front and rear positions to beproximate to said front open end and said rear open end, respectively,said front holding portion holding said rear connecting end of saidneedle cannula such that when said rear shell portion is in the frontposition, said needle cannula is placed in a position of use, where saidfront segment extends forwardly of said front open end for ready use,and when said rear shell portion is in the rear position, said needlecannula is placed in a disposal position, where said front segmentretreats into said passage, said rear shell portion surrounding the axisand defining a flashback chamber which is fluidly communicated with saidneedle cannula, said needle hub further including an interconnectingportion which is formed integrally with and which extends forwardly fromsaid rear shell portion along the axis and which defines an axialpassageway that extends therethrough and that is communicated with saidflashback chamber, and a sleeve portion which is integrally formed withand which extends rearwardly from said front holding portion along theaxis and which is detachably sleeved on said interconnecting portionfrom said front open end of said barrel along the axis so as to fluidlycommunicate said needle cannula with said flashback chamber; areleasably retaining member which is disposed to arrest axial movementof said needle hub relative to said barrel when said rear shell portionis in the front position, and which includes a retaining hole formed insaid outer barrel wall surface of said larger-diameter wall portion, andextending in a radial direction through said inner barrel wall surface,and an engaging peg disposed to extend in the radial direction, andengageable in said retaining hole to establish an interengagementbetween said larger-diameter wall portion and said rear shell portionsuch that movement of said rear shell portion at the front position isarrested; an actuator operable externally and disposed to enable saidengaging peg to be disengaged from said retaining hole so as to permitthe axial movement of said needle hub to the rear position; a catheterhub including a sleeve portion which is detachably sleeved on said frontholding portion of said needle hub and which defines a duct along theaxis, and a tip portion which is opposite to said sleeve portion alongthe axis, and which defines a through hole that is communicated withsaid duct along the axis and that permits extension of said frontsegment therethrough; and a tubular catheter having a proximate segmentwhich is inserted into said through hole and which extends along theaxis to be fluidly communicated with said duct, and a distal segmentwhich extends from said proximate segment along the axis to extendforwardly of said tip portion so as to surround and sheathe said frontsegment of said needle cannula while permitting said tip end to projectforwardly of said distal segment when said needle cannula is placed inthe position of use.
 17. The intravenous catheter introducing device ofclaim 16, further comprising a biasing member which is interposedbetween said rear shell portion and said inner barrel wall surface, andwhich is disposed to bias said needle hub toward the rear position.